US10982668B2 - Linear compressor and method for controlling linear compressor - Google Patents
Linear compressor and method for controlling linear compressor Download PDFInfo
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- US10982668B2 US10982668B2 US15/857,369 US201715857369A US10982668B2 US 10982668 B2 US10982668 B2 US 10982668B2 US 201715857369 A US201715857369 A US 201715857369A US 10982668 B2 US10982668 B2 US 10982668B2
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
- F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/06—Control using electricity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/0005—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00 adaptations of pistons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/12—Casings; Cylinders; Cylinder heads; Fluid connections
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/06—Control using electricity
- F04B49/065—Control using electricity and making use of computers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/12—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by varying the length of stroke of the working members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B17/00—Systems involving the use of models or simulators of said systems
- G05B17/02—Systems involving the use of models or simulators of said systems electric
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2201/00—Pump parameters
- F04B2201/02—Piston parameters
- F04B2201/0201—Position of the piston
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/04—Motor parameters of linear electric motors
- F04B2203/0401—Current
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/04—Motor parameters of linear electric motors
- F04B2203/0402—Voltage
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2207/00—External parameters
- F04B2207/04—Settings
- F04B2207/046—Settings of length of piston stroke
Definitions
- the present disclosure relates to a linear compressor and a method for controlling the same, and particularly, to a linear compressor controlling movement of a piston without using a separate sensor, and a method for controlling the same.
- a compressor a device for converting mechanical energy into compressive energy of a compressible fluid
- a refrigerating machine for example, a refrigerator or an air conditioner.
- Compressors are classified as a reciprocating compressor, a rotary compressor, and a scroll compressor.
- a reciprocating compressor a compression space in which a working gas is sucked or discharged is formed between a piston and a cylinder, and the piston linearly reciprocates within the cylinder to compress a refrigerant.
- a compression space in which a working gas is sucked or discharged is formed between an eccentrically rotating roller and a cylinder so that a refrigerant is compressed as the cylinder eccentrically rotates along an inner wall of the cylinder.
- a compression space in which a working gas is sucked or discharged is formed between an orbiting scroll and a fixed scroll so that a refrigerant is compressed as the orbiting scroll rotates along the fixed scroll
- the reciprocating compressor sucks, compresses, and discharges a refrigerant gas by linearly reciprocating the internal piston within the cylinder.
- the reciprocating compressor is classified as a recipro-type and a linear type depending on a way in which the piston is driven.
- the recipro scheme is that a crankshaft is coupled to a rotary motor and a piston is coupled to the crankshaft to convert a rotational motion of the motor into a linear reciprocating motion.
- the linear scheme is that a piston is connected to a mover of a motor that linearly moves to reciprocate the piston by a rectilinear motion of the motor.
- Such a reciprocating compressor includes a driving unit generating a driving force and a compression unit compressing a fluid upon receiving the driving force from the electric unit.
- a motor is generally used as the electric unit, and in the case of the linear scheme, a linear motor is used.
- the linear motor directly generates a linear driving force by itself, it does not require a mechanical conversion device a structure thereof is not complicated.
- the linear motor has features that can reduce loss due to energy conversion and greatly reduce noise because there is no joint where friction and abrasion occur.
- a linear type reciprocating compressor hereinafter referred to as a linear compressor
- a compression ratio may be changed by changing a stroke voltage applied to the linear compressor, and thus, the linear compressor may also be used to variably control freezing capacity.
- the linear compressor reciprocates in a state in which a piston is not mechanically restrained within a cylinder, if an excessive voltage is applied suddenly, the piston may collide with a cylinder wall or the piston may not move forward due to a large load, resulting in failure of compression.
- a control device for controlling the motion of the piston with respect to the load variation or the voltage variation is essential.
- a compressor control device performs feedback control by detecting a voltage and a current applied to a compressor motor and estimating a stroke in a sensorless manner.
- the compressor control device includes a triac or an inverter as means for controlling a compressor.
- a position of the piston at the initial stage of driving and a position of the piston in the middle of driving may be different.
- an aspect of the detailed description is to provide a linear compressor capable of detecting an absolute position of a piston without a separate sensor, and a method for controlling the same.
- Another aspect of the detailed description is to provide a linear compressor which performs a highly efficient operation, while reducing noise of the linear compressor, and a method for controlling the same.
- Another aspect of the detailed description is to provide a linear compressor in which occurrence of noise is reduced and manufacturing cost is reduced.
- a linear compressor includes: a piston reciprocating within a cylinder; a motor providing a driving force for movement of the piston; a sensing unit sensing a motor voltage and a motor current related to the motor; a discharge part installed at one end of the cylinder and adjusting discharge of a refrigerant compressed within the cylinder; and a controller detecting a load variation of the motor using at least one of the motor voltage and the motor current, calculating a compensation value related to a position of the piston each time a load variation of the motor is detected, and detecting an absolute position of the piston using the calculated compensation value.
- the controller may estimate a stroke of the piston using the motor voltage and the motor current, and calculate a distance over which the piston was pushed from an initial position of the piston before driving of the linear compressor starts, on the basis of the estimated stroke.
- the controller may calculate a distance between a top dead center (TDC) of the piston and the discharge part using the estimated stroke and the calculated pushed distance.
- TDC top dead center
- the controller may calculate a parameter related to movement of the piston in real time using the estimated stroke and the detected motor current, calculate a distance between the TDC of the piston and the discharge part at the time point when the calculated parameter forms a point of inflection, and calculate the compensation value by comparing the calculated distance with a preset reference distance.
- the controller may re-calculate the distance between the TDC of the piston and the discharge part on the basis of the calculated compensation value.
- the controller may control the motor such that the distance between the TDC of the piston and the discharge part is maintained at a distance equal to or shorter than a preset limit distance.
- the controller may detect an operation rate of the motor, and determine whether a load variation of the motor has occurred on the basis of the detected operation rate.
- the controller may calculate the compensation value related to the position of the piston.
- the controller may calculate the compensation value related to the position of the piston.
- the controller may detect a phase difference between the estimated stroke and the motor current, and calculate the distance over which the piston was pushed using the detected phase difference.
- the controller may calculate a first parameter and a second parameter using the phase difference and calculate the pushed distance of the piston using the first parameter, the second parameter, and the stroke.
- a linear compressor includes: a piston reciprocating within a cylinder; a motor providing a driving force for movement of the piston; a sensing unit sensing a motor voltage and a motor current related to the motor; a discharge part installed at one end of the cylinder and adjusting discharge of a refrigerant compressed within the cylinder; and a controller detecting a load variation of the motor using at least one of the motor voltage and the motor current, detecting an absolute position of a top dead center (TDC) of the piston when an amount of the detected load variation is included in a predetermined range, and controlling the motor on the basis of the detected absolution position of the TDC.
- TDC top dead center
- the controller may control the motor such that the detected absolute position of the TDC falls within a predetermined distance interval from the discharge part.
- the linear compressor may further include: a memory storing information related to mechanical characteristics of the linear compressor, wherein the controller may detect an initial position of the piston on the basis of the information related to the mechanical characteristics of the linear compressor and detect an absolute position of a TDC of the piston on the basis of the initial position of the piston.
- the controller may estimate a stroke of the piston using the sensed motor voltage and motor current during driving of the linear compressor, and detect a distance over which the piston was pushed in a direction opposite to one side where the discharge part is installed, from the initial position of the piston on the basis of the estimated stroke.
- the controller may detect an absolute position of the TDC of the piston on the basis of the detected pushed distance and the initial position of the piston.
- the controller may calculate at least one of an error of the estimated stroke value and an error of the detected pushed distance, and update the absolute position of the TDC of the piston by reflecting the calculated error.
- the linear compressor and the method for controlling the same according to the present invention have an advantage in that noise generated in the linear compressor may be reduced by reducing a collision force between the piston and the discharge valve. Also, according to the present invention, since collision between the piston and the discharge valve is prevented, wear of the piston and the discharge valve due to a collision may be reduced, increasing a lifespan of the mechanism and components.
- FIG. 1A is a conceptual diagram showing an example of a general recipro-type reciprocating compressor.
- FIG. 1B is a conceptual view showing an example of a general linear type reciprocating compressor.
- FIGS. 1C-1D are graphs relating to various parameters used for controlling a top dead center of a linear compressor.
- FIG. 2 is a block diagram showing components of a linear compressor
- FIG. 3 is a cross-sectional view showing an embodiment of a linear compressor according to the present invention.
- FIG. 4 is a conceptual diagram showing an embodiment of a linear compressor according to the present invention.
- FIG. 5 is a conceptual diagram showing a control process of a linear compressor according to the present invention in an s-domain.
- FIG. 6 is a flow chart showing a method for controlling a linear compressor according to the present invention.
- FIG. 7 is a flow chart showing a method for controlling a linear compressor according to the present invention.
- the invention disclosed in this specification can be applied to a control device of a linear compressor and a method for controlling a linear compressor.
- the invention disclosed in this specification is not limited thereto and can be applied to all existing compressor control devices, compressor control methods, motor control devices, motor control methods, noise test devices for motors.
- the motor provided in the reciprocating compressor can be combined with a crankshaft 1 a , whereby a rotational motion of the motor can be converted into a linear reciprocating motion.
- the piston provided in the recipro-type compressor can perform a linear reciprocating motion within a predetermined position range according to a specification of the crankshaft or a specification of a connecting rod connecting the crankshaft and the piston.
- the discharge part 2 a installed in the recipro-type compressor can be fixedly installed with respect to the cylinder.
- the discharge part 2 a may be formed as a valve plate.
- the recipro-type compressor has a problem in that friction occurs among the crankshaft, the connecting rod, and the piston, and therefore, there are more element which generates friction than those of the linear type compressor.
- FIGS. 1C-1D illustrate graphs relating to various parameters used for controlling a top dead center of a linear type reciprocating compressor.
- the linear type compressor is a compressor in which the piston reciprocates by a linear motion of the motor by connecting the piston to a mover of the motor which linearly moves.
- an elastic member 1 b may be connected between the cylinder of the linear type compressor and the piston.
- the piston can perform a linear reciprocating motion by the linear motor, and the controller of the linear compressor can control the linear motor to change a direction of motion of the piston.
- the controller of the linear compressor shown in FIG. 1B may determine a time point at which the piston collides with the discharge part 2 b as a time point at which the piston has reached the top dead center (TDC), whereby the controller may control the linear motor to change a movement direction of the piston.
- TDC top dead center
- FIG. 1C a graph associated with the general linear compressor is illustrated. Specifically, as shown in FIG. 1C , a phase difference between a motor current (i) and a stroke (x) of the piston forms a point of inflection at a time point when the piston reaches the TDC.
- the controller of the general linear compressor detects the motor current (i) using a current sensor, detects a motor voltage (not shown) using a voltage sensor, and estimates the stroke (x) based on the motor current and the motor voltage. Accordingly, the controller can calculate the phase difference ( ⁇ ) between the motor current (i) and the stroke (x), and when the phase difference ( ⁇ ) forms the point of inflection, the controller may determine that the piston has reached the TDC, and at this time, the controller may control the linear motor such that the movement direction of the piston is changed.
- control the motor such that the piston does not exceed the TDC to prevent the controller of the linear compressor from colliding with the discharge part disposed at one end of the cylinder will be defined as “conventional TDC control”.
- the conventional TDC control is as follows.
- the controller of the linear compressor can calculate a gas constant (Kg) related to a reciprocating motion of the piston in real time using the detected motor current and the estimated stroke.
- Kg gas constant
- the controller can calculate the gas constant (Kg) using the following equation (1).
- k g ⁇ ⁇ ⁇ I ⁇ ( j ⁇ ⁇ w ) X ⁇ ( j ⁇ ⁇ w ) ⁇ ⁇ cos ⁇ ( ⁇ i , x ) + m ⁇ ⁇ w 2 - k m [ Equation ⁇ ⁇ 1 ]
- I(jw) denotes a peak value of one-period current
- X(jw) denotes a peak value of one-cycle stroke
- a denotes a motor constant or a counter electromotive force constant
- ⁇ i,x denotes a phase difference between current and stroke
- m denotes a movement mass of the piston
- w denotes an operating frequency of the motor
- Km denotes a mechanical spring constant.
- Equation 2 related to a gas constant (Kg) is derived by the above equation.
- the calculated gas constant (Kg) may be proportional to the phase difference between the motor current and the stroke.
- the controller of the linear compressor can determine that the piston reaches the TDC when the gas constant (Kg) or the phase difference forms a point of inflection.
- the general linear compressor that performs the TDC control as described above may have the discharge part 2 b having an elastic member.
- the discharging part 2 b provided in the related art linear compressor is connected to an elastic member having a relatively weak elastic force. In this case, since a repulsive force of the discharge part 2 b and the piston is relatively weak, the compression state within the cylinder is unstable.
- an elastic member having a considerably increased repulsive force may be connected to the discharge part 2 b .
- a force by which the discharge part 2 b adheres to the cylinder is increased, and thus, when the piston and the discharge part 2 b collide with each other, a repulsive force generated between the discharge part 2 b and the piston is stronger than that of the related art linear compressor.
- a discharge part having a valve plate may be included at one end of the cylinder.
- the linear compressor including the discharge part formed with the valve plate since the cylinder and the valve plate are fixedly coupled to each other, a repulsive force generated between the valve plate and the piston is stronger than that of the related art linear compressor.
- the movement of the piston can be controlled without additionally using a separate sensor in the linear compressor of the present invention.
- the controller of the linear compressor performing the TDC control according to the present invention may calculate a stroke of the piston using the detected motor voltage and the motor current.
- the controller may control the motor such that the piston does not collide with the valve plate on the basis of a change in the calculated stroke.
- the controller of the linear compressor according to the present invention may continuously estimate the stroke of the piston while the piston reciprocates within the cylinder, to detect a change in the estimated stroke.
- the estimated stroke and the actual stroke form a proportional relationship until the piston collides with the discharge part provided at one end of the cylinder.
- the estimated stroke and the actual stroke form an inverse relationship with each other.
- the estimated stroke and the actual stroke can form the inverse relationship from the point of time of collision.
- FIG. 2 is a block diagram showing a configuration of a control device for a reciprocating compressor according to an embodiment of the present invention.
- the controller of the reciprocating compressor may include a sensing unit that senses a motor voltage and a motor current associated with the motor.
- the sensing unit may include a voltage detecting unit 21 detecting a motor voltage applied to the motor, and a current detecting unit 22 detecting a motor current applied to the motor.
- the voltage detecting unit 21 and the current detecting unit 22 can transmit information related to the detected motor voltage and the motor current to the controller 25 or a stroke estimating unit 23 .
- the compressor or a control device of the compressor according to the present invention includes the stroke estimating unit 23 estimating a stroke by the detected motor current and motor voltage and a motor parameter, a comparator 24 comparing the stroke estimation value with a stroke reference value and outputting a difference according to a comparison result, and a controller 25 controlling the stroke by varying a voltage applied to the motor according to the difference.
- the components of the control device shown in FIG. 2 are not essential, and thus, a compressor control device having greater or fewer components can be implemented.
- the compressor control device may be applied to a reciprocating compressor, but in this disclosure, it will be described herein with reference to a linear compressor.
- the voltage detecting unit 21 detects a motor voltage applied to the compressor motor.
- the voltage detecting unit 21 may include a rectifying unit and a DC link unit.
- the rectifying unit may rectify an AC power having a predetermined voltage to output a DC voltage
- the DC link unit 12 may include two capacitors.
- the current detecting unit 22 which detects a motor current applied to the motor, may sense a current flowing in a coil of the compressor motor according to an embodiment.
- the stroke estimating unit 23 can calculate a stroke estimation value using the detected motor current and the motor voltage and the motor parameters, and apply the calculated stroke estimation value to the comparator 24 .
- the stroke estimating unit 23 can calculate the stroke estimation value through Equation 3 below.
- x denotes a stroke
- ⁇ denotes a motor constant or counter electromotive force constant
- Vm denotes a motor voltage
- im denotes a motor current
- R denotes resistance
- L denotes inductance
- the comparator 24 may compare the stroke estimation value with the stroke reference value and applies a corresponding difference signal to the controller 25 , whereby the controller 25 may control the stroke by varying the voltage applied to the motor.
- the controller 25 decreases the voltage applied to the motor when the stroke estimation value is larger than the stroke reference value, and increases the voltage applied to the motor when the stroke estimation value is smaller than the stroke reference value.
- the controller 25 and the stroke estimating unit 23 may be formed as one unit. That is, the controller 25 and the stroke estimating unit 23 may correspond to a single processor or a computer.
- FIG. 3 is a cross-sectional view of a linear compressor according to the present invention.
- the linear compressor according to an embodiment of the present invention may be a linear compressor to which a linear compressor control device or a compressor control device is applicable, regardless of type or form of a linear compressor.
- the linear compressor according to one embodiment of the present invention shown in FIG. 3 is merely illustrative and is not intended to limit the scope of the present invention.
- a motor applied to a compressor is provided with a winding coil installed on a stator and a magnet installed on a mover, so that the mover rotates or reciprocates according to interaction between the winding coil and the magnet.
- the winding coil can be formed variously according to motor types.
- a winding coil may be wound as a concentrated winding or a distributed winding around a plurality of slots formed in a circumferential direction on an inner circumferential surface of the stator, and in the case of a reciprocating motor, a coil is wound in an annular shape to form a winding coil and a plurality of core sheets are inserted and coupled to an outer circumferential surface of the winding coil in a circumferential direction.
- a winding coil is formed by winding the coil in an annular shape, generally, a coil is wound around an annular bobbin formed of a plastic material to form a winding coil.
- the reciprocating compressor has a structure in which a frame 120 is resiliently installed by a plurality of support springs 161 and 162 in an inner space of a closed shell 110 .
- a suction pipe 111 connected to an evaporator (not shown) of the refrigerating cycle is connected to an internal space of the shell 110 , and a discharge pipe 112 connected to a condenser (not shown) of the refrigerating cycle device is installed on one side of a suction pipe 111 in a communicating manner.
- An outer stator 131 and an inner stator 132 of a reciprocating motor 130 constituting a motor unit M are fixedly mounted in the frame 120 and a mover 133 making a reciprocating motion is provided between the outer stator 131 and the inner stator 132 .
- a piston 142 constituting a compression part Cp together with a cylinder 141 (to be described later) is coupled to the mover 133 of the reciprocating motor 130 to perform a reciprocating motion.
- the cylinder 141 is provided within a range in which the cylinder 141 overlaps with the stators 131 and 132 of the reciprocating motor 130 in an axial direction.
- a compression space CS 1 is formed in the cylinder 141 and a suction flow channel F guiding a refrigerant to the compression space CS 1 is formed in the piston 142 .
- the suction valve 143 for opening and closing the suction flow channel F is formed at an end of the suction flow channel F, and a discharge valve 145 for opening and closing the compression space CS 1 of the cylinder 141 is installed at a front end surface of the cylinder 141 .
- a discharge part of the linear compressor according to the present invention may be formed in various forms.
- the linear compressor according to the present invention may include a discharge part formed as a valve plate. That is, the discharge part used in the conventional recipro-type compressor can be applied to the linear compressor according to the present invention.
- the linear compressor according to the present invention may include a discharge part having an elastic member as illustrated in FIG. 1B . That is, the discharge part which has been used in the existing linear compressor may also be applied to the linear compressor according to the present invention.
- an elastic force of the elastic member provided in the discharging part of the linear compressor according to the present invention may be greater than the elastic force of the elastic member provided in a general linear compressor.
- FIG. 4 illustrates an embodiment of a method for controlling a linear compressor according to the present invention.
- a distance between a central position of the piston and the discharge part within the cylinder before the linear compressor is driven is defined as X0.
- a distance between the TDC of the piston and the discharge part is defined as XTDC.
- a distance between the TDC and a BDC of the piston is defined as Stk.
- a distance over which the central position of the piston is pushed within the cylinder after the linear compressor is driven is defined as Xdc.
- a distance between the TDC of the piston and the discharge part is defined as Xv.
- Xv may be a constant set according to the design of the compressor.
- Xv when the control parameter corresponds to the gas constant (Kg), a point of inflection of the gas constant (Kg) theoretically occurs when the piston comes into contact with the discharge part, so that Xv can be set to zero.
- Xv is not limited thereto and can be set to be different according to the design of the compressor or a change in the control parameter.
- the distance (XTDC) between the TDC of the piston and the discharge part can be calculated by the Equation 4 below.
- X TDC_C X TDC +( X V ⁇ X V_obj ) [Equation 5]
- XTDC_C denotes an updated value of the XTDC.
- Xv_obj denotes XTDC calculated at the time when the control parameter forms a point of inflection.
- the controller 25 of the linear compressor according to the present invention can detect a load variation of the motor using at least one of the motor voltage and the motor current.
- the controller 25 may calculate a compensation value related to a position of the piston whenever a load variation of the motor is detected, and may control an absolute position of the piston using the calculated compensation value.
- the controller 25 can estimate a stroke of the piston using the motor voltage and the motor current, and on the basis of the estimated stroke, the controller 25 may calculate the distance Xdc over which the piston was pushed, from an initial position of the piston before the linear compressor starts to be driven.
- the controller 25 can calculate the distance XTDC between the TDC of the piston and the discharge part using the estimated stroke and the calculated pushed distance Xdc.
- the controller 25 can calculate a parameter related to the movement of the piston in real time using the estimated stroke and the detected motor current.
- the controller 25 can calculate the distance XTDC between the TDC of the piston and the discharge part at the time when the calculated parameter forms the point of inflection.
- the controller 25 can compare XTDC at the time when the parameter forms the point of inflection with a predetermined reference distance and calculate the compensation value on the basis of a comparison result.
- the controller 25 may control the motor to maintain the distance XTDC between the TDC of the piston and the discharge part at a distance equal to or shorter than a predetermined limit distance.
- the controller 25 may increase the stroke reference value or increase the motor voltage or the motor current
- the controller 25 can detect an operation rate of the motor and determine whether or not load of the motor fluctuates on the basis of the detected operation rate.
- the controller 25 can determine a load variation of the motor in various manners in addition to the operation rate. That is, when a user input for changing the output of the linear compressor is applied, the controller 25 can determine that a load variation of the motor occurs.
- the controller 25 can calculate a compensation value related to the position of the piston at the time of initial driving of the motor.
- the compensation value related to the position of the piston may include an error of the stroke (Stk) estimation value and an error of the calculation result of the distance (Xdc) over which the piston was pushed from the initial position.
- the controller 25 may calculate a compensation value related to the position of the piston at the initial starting of the motor or whenever the load of the motor is varied, in order to reduce an error which may occur.
- a specific method of calculating the compensation value by the controller 25 is as follows.
- the controller 25 can calculate the distance XTDC between the TDC of the piston and the discharge part. That is, the controller 25 can calculate the XTDC at a first time point.
- the controller 25 can monitor a change in the control parameter (e.g., the gas constant (Kg)) related to the movement of the piston used in the conventional TDC control.
- Kg gas constant
- the controller 25 can calculate the distance XTDC between the TDC of the piston and the discharge part at a second time point at which the control parameter forms the point of inflection during monitoring.
- a theoretical position of the piston at the time when the control parameter forms the point of inflexion is defined as Xv
- XTDC calculated at the second time point is defined as Xv_obj.
- the controller 25 can calculate a final XTDC by adding the resultant value obtained by subtracting Xv_obj from Xv to XTDC at the first time point. That is, the controller 25 can calculate the compensation value related to the position of the piston by subtracting Xv_obj from Xv.
- the controller 25 can calculate the compensation value related to the position of the piston even when a load fluctuation amount of the motor is equal to or less than a predetermined value for a predetermined time interval. That is, even when the load of the motor is maintained for a considerable period of time, the controller 25 can update XTDC by calculating a compensation value related to the position of the piston.
- the controller 25 can detect a phase difference between the estimated stroke and the motor current, and calculate the pushed distance Xdc of the piston using the detected phase difference.
- the controller 25 can calculate the pushed distance Xdc of the piston using a predetermined equation including the phase difference between the estimated stroke and the motor current as variables.
- the controller 25 may calculate the gas constant Kg and the damping constant Cg using the phase difference, and calculate the pushed distance Xdc of the piston using the gas constant, the damping constant, and the stroke have. That is, the controller 25 may calculate the pushed distance Xdc of the piston using the predetermined equation including the gas constant Kg, the damping constant Cg, and the stroke Stk, as variables.
- the controller 25 of the linear compressor according to the present invention can detect an absolute position of the TDC of the piston.
- the controller 25 can control the motor on the basis of the detected absolute position of the TDC.
- the controller 25 can compare the detected absolute position of the TDC and the stroke reference value, and adjust the motor voltage on the basis of a comparison result.
- the controller 25 can control the motor such that the detected absolute position of the TDC falls within a predetermined distance from the discharge part.
- the controller 25 may further include a memory (not shown) storing information related to mechanical characteristics of the linear compressor.
- the controller 25 may detect an initial position of the piston on the basis of the information related to the mechanical characteristics of the linear compressor and detect the absolute position of the TDC of the piston on the basis of the initial position of the piston.
- the information related to the mechanical characteristics of the linear compressor may include information related to standard of the cylinder of the linear compressor, the piston, and a spring provided in the piston or information related to an initial installation position of the piston within the cylinder.
- the controller 25 may estimate the stroke Stk of the piston using the sensed motor voltage and the motor current during driving of the linear compressor and detect the distance Xdc over which the piston is pushed in a direction opposite to one side where the discharge part is installed within the cylinder, from the initial position of the piston on the basis of the estimated stroke.
- the controller 25 can detect the absolute position of the TDC of the piston on the basis of the detected pushed distance Xdc and the initial position of the piston.
- the controller 25 may calculate at least one of an error of the estimated stroke value and an error of the detected pushed distance Xdc and update the absolute position of the TDC of the piston by reflecting the calculated error.
- FIG. 6 an embodiment of a method for controlling a linear compressor according to the present invention is described.
- the controller 25 can generate a stroke reference value having a predetermined value and calculate the distance XTDC between the TDC of the piston and the discharge part (S 602 ).
- the controller 25 can compare the stroke reference value and the XTDC (S 603 ), and adjust the motor voltage on the basis of a comparison result (S 604 ).
- FIG. 7 another embodiment of the method for controlling a linear compressor according to the present invention is described.
- the controller 25 can calculate XTDC at an arbitrary first time point (S 701 ).
- the controller 25 may monitor a control parameter related to the movement of the piston during the driving of the compressor (S 702 ). During the monitoring of the control parameter, the controller 25 may again calculate the XTDC at a second time point at which the control parameter forms a point of inflection (S 703 ).
- the controller 25 may compare the XTDC calculated at the first time point and the XTDC calculated at the second time point to determine a final XTDC (S 704 ).
- the controller 25 may compare the final XTDC value with the stroke reference value (S 705 ), and adjust the motor voltage on the basis of a comparison result (S 706 ).
- the linear compressor and the method for controlling a linear compressor according to the present invention have an advantage in that noise generated in the linear compressor may be reduced by reducing a collision force between the piston and the discharge valve. Also, according to the present invention, since collision between the piston and the discharge valve is prevented, wear of the piston and the discharge valve due to a collision may be reduced, increasing a lifespan of the mechanism and components.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Control Of Positive-Displacement Pumps (AREA)
- Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
Abstract
Description
X TDC_C =X TDC+(X V −X V_obj) [Equation 5]
Claims (17)
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KR1020160184417A KR102454719B1 (en) | 2016-12-30 | 2016-12-30 | Linear compressor and method for controlling linear compressor |
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US20070196214A1 (en) | 2006-02-21 | 2007-08-23 | Cesare Bocchiola | Sensor-less control method for linear compressors |
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KR100742041B1 (en) * | 1999-12-23 | 2007-07-23 | 월풀 에쎄.아. | Method of controlling a compressor, piston position monitoring system and compressor |
KR100408068B1 (en) * | 2001-07-31 | 2003-12-03 | 엘지전자 주식회사 | Stroke comtrol apparatus for reciprocating compressor |
KR101299548B1 (en) * | 2011-06-13 | 2013-08-23 | 엘지전자 주식회사 | Apparatus for controlling compressor and method of the same |
-
2016
- 2016-12-30 KR KR1020160184417A patent/KR102454719B1/en active IP Right Grant
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- 2017-12-28 EP EP17210854.0A patent/EP3343037B1/en active Active
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WO2000079671A1 (en) | 1999-06-21 | 2000-12-28 | Fisher & Paykel Limited | Linear motor |
EP1469580A1 (en) | 2003-04-14 | 2004-10-20 | Matsushita Electric Industrial Co., Ltd. | Motor driving apparatus for a linear vibration motor |
US20070196214A1 (en) | 2006-02-21 | 2007-08-23 | Cesare Bocchiola | Sensor-less control method for linear compressors |
WO2007123323A1 (en) | 2006-04-20 | 2007-11-01 | Lg Electronics Inc. | Driving control apparatus and method for linear compressor |
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KR102454719B1 (en) | 2022-10-14 |
KR20180079053A (en) | 2018-07-10 |
EP3343037A1 (en) | 2018-07-04 |
US20180195509A1 (en) | 2018-07-12 |
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